---
cve: "CVE-2026-80557"
severity: "CRITICAL"
cvss: 9.8
epss: "68.2%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-08-26 15:17:10"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-05T08:42:06+02:00"
---

# CVE-2026-80557

> 9.8 CRITICAL

## Beschreibung

In the Linux kernel, the following vulnerability has been resolved:

libceph: fix OOB read in decode_watchers() via missing bounds check

ceph_start_decoding() validates that struct_len bytes remain in the
buffer after the encoding header, but accepts struct_len=0 as valid:
ceph_decode_need(p, end, 0, bad) always passes. When a malicious or
compromised OSD sends an obj_list_watch_response_t reply with
struct_len=0, ceph_start_decoding() returns success with p == end,
leaving zero bytes guaranteed for subsequent reads.

The immediately following ceph_decode_32(p) in decode_watchers() has
no preceding bounds check. With p == end this is a 4-byte read past
the validated buffer boundary. The garbage value is then passed
directly to kzalloc_objs() as the watcher count.

The sibling function decode_watcher() already uses the safe variants
(ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32)
after its own ceph_start_decoding() call. decode_watchers() is the
only site that uses the bare variant, confirming an oversight.

Fix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end,
*num_watchers, bad), consistent with the established pattern.

Attacker model: a malicious or compromised OSD in a multi-tenant Ceph
deployment (e.g. cloud) can trigger this against any kernel client
that calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges
beyond OSD session establishment.

[ idryomov: trim changelog ]

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 5.10.267
- Kernel ≥ 5.15.218
- Kernel ≥ 6.1.185
- Kernel ≥ 6.6.154
- Kernel ≥ 6.12.106
- Kernel ≥ 6.18.47
- Kernel ≥ 7.1.10

## Referenzen

- <https://git.kernel.org/stable/c/00ead17c7de137a692edee59f2772e6af687e8eb>
- <https://git.kernel.org/stable/c/1c824e7c75bb4adf19553dd4ea944a5d83096be8>
- <https://git.kernel.org/stable/c/7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1>
- <https://git.kernel.org/stable/c/85479b7d65b4ebcb07fbbe57230976793974ab4a>
- <https://git.kernel.org/stable/c/c59219a6b62d74936963983e5815524c3de8dd79>
- <https://git.kernel.org/stable/c/cb8246e5846dbbe34930903a90c7a90dd8e5910b>
- <https://git.kernel.org/stable/c/eab3eeb68bfc639d74f27256f05546af5c4f787d>
- <https://git.kernel.org/stable/c/f161be39201eb5f9b1f58fb8f90b8a9cd3931eb6>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-80557) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_